Question: Which of these numbers is composite? ${31,\ 37,\ 65,\ 67,\ 89}$
Answer: A composite number is a number that has more than two factors (including 1 and itself). 31, 37, 67, and 89 each have only two factors. The factors of 65 are 1, 5, 13, and 65. Thus, 65 is the composite number.